1. Field of the Invention
The present invention relates generally to an optical read and write apparatus, and more particularly to an optical read and write apparatus that is capable of correcting the difference between the phases of an object lens and a turntable by freely adjusting the position of an optical pickup in the direction perpendicular to the direction of transfer.
2. Description of the Prior Art
In general, an optical read and write apparatus is an apparatus that reads and/or writes information from/onto a disk using an optical system.
In such an optical read and write apparatus, when an optical disk is placed on a turntable and rotated at a certain speed by a spindle motor, an optical pickup reads optical signals from or writes information onto the optical disk by irradiating a laser beam onto the optical disk while reciprocating in the radial direction of the optical disk.
With reference to FIG. 1, the deck base assembly of a conventional optical read and write apparatus is described below. An opening 1a is formed in the center portion of a deck base 1, a spindle motor 2 is mounted on one side of the deck base 1 in the vicinity of the opening 1a, and a turntable 3 on which an optical disk “D” is placed is coupled to and rotatably supported by the shaft of the spindle motor 2.
A main shaft 6 and an secondary shaft 6′ are arranged to be parallel to each other across the opening 1a, and the ends of the shafts 6 and 6′ are supported by support members 7 fastened to the deck base 1 to be tilted.
An optical pickup 5 equipped with an object lens 5a is engaged with the main shaft 6 and the secondary shaft 6′, and supported to be moved along the main shaft 6 and the secondary shaft 6′ by a gear train 8.
However, the convention optical read and write apparatus constructed as described above requires technologies for minimizing a phase error so as to improve optical performance.
In this case, the phase error means a difference between the distance from the main shaft 6 to the center of the object lens 5a (or a point on which a light beam is focused) and the distance from the main shaft 6 to the center of the turntable 3 generated by various causes, even though the distances must be kept equal.
Accordingly, the conventional optical read and write apparatus is problematic in that the phase error occurs due to various causes, such as the deformation of component parts and the allowance of assembly.
In more detail, the phase difference occurs when the component parts are assembled into an optical pickup.
That is, when the focus of a light beam is adjusted by rotating a laser diode or changing the position of an object lens, component parts are bonded and bonding material is solidified, the position of the laser diode or object lens is undesirably changed frequently, so the focus of the light beam is undesirably changed, thus causing-the phase error.
Another cause of the phase error is an assembly error that occurs when a spindle motor is attached to a deck base or an optical pickup is attached to a main shaft and a secondary shaft.
Another cause of the phase difference occurs when a tilt (or skew) is adjusted.
When an optical disk and an object lens are parallel with each other, a light beam is correctly focused at a position on an optical disk, so optical performance is efficiently implemented. In practice, the optical disk or the object lens is tilted for various reasons and, therefore, the optical disk and the object lens are not parallel with each other. The adjustment of a tile is performed to cause the optical disk and the object lens to be parallel with each other by adjusting the tilt of an optical pickup.
One of methods of adjusting the tilt of an optical pickup is to adjust the tilt of the optical pickup by adjusting the heights or tilts of a main shaft and a secondary shaft. Meanwhile, when the tilt of the optical pickup is adjusted as described above, the position of the optical pickup is changed in proportion to the adjusted tilt of the optical pickup, so the phase error occurs.
As described above, the conventional optical write and read apparatus undergoes the phase error for various reasons, so errors occur when the optical pickup operates, thus deteriorating the reliability of a product.